L-carnitine is known as vitamin B.sub.T and chemically termed L-.gamma.-amino-.beta.-hydroxybutyric acid trimethylbetain.
L-carnitine known as vitamin B.sub.T exists in tissues of many living organisms, including microorganism to human being, and is an indispensable factor for the growth of dark mealworm (Tanebrio obscurus Fabricius). For this reason, various studies have recently been made with regard to its physiological activities and clinical application (See S. L. De Felice, Orphan Drugs, F. E. Karch, Ed. C. Marcel Dekker, New York, 1982, pp. 33-56). Under such circumstances, it has already been known that D-carnitine competitively inhibits the physiological activities of L-carnitine, though carnitine has been synthesized as DL-carnitine chloride on an industrial scale. Therefore, an effective method of resolving DL-carnitine has been desired.
In this connection, a method of optical resolution of DL-carnitine has been disclosed in East German Patent No. 93347 specification, wherein L(+)tartaric acid, dibenzoyl-D(-)tartaric acid, D(+)camphoric acid and D(-)camphoric acid are recited as resolving agents. This prior art method, however, involves a problem in its application to industrial production of L-carnitine, because the resolving agents used therein are relatively expensive and L-carnitine of high purity is difficult to obtain.